Weight Loss Calculator

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weight loss calculator
Daily Calories for Specific GoalMaintenance Calories (TDEE)
MaleFemale
Sedentary (Little/No Exercise)Lightly Active (1-3 days/week)Moderately Active (3-5 days/week)Very Active (6-7 days/week)Extra Active (Hard Labor/2x Training)
Results:
Enter details to see your target calories.
© Weight Loss Calculator
function calculateWeightLoss(){var gender=document.getElementById('gender').value;var age=parseFloat(document.getElementById('age').value);var weightLbs=parseFloat(document.getElementById('weight').value);var heightIn=parseFloat(document.getElementById('height').value);var activity=parseFloat(document.getElementById('activity').value);var lossGoal=parseFloat(document.getElementById('loss_goal').value);var weeks=parseFloat(document.getElementById('weeks').value);var showSteps=document.getElementById('steps').checked;var calcType=document.getElementById('calc_type').value;if(isNaN(age)||isNaN(weightLbs)||isNaN(heightIn)||isNaN(lossGoal)||isNaN(weeks)){alert('Please fill in all numeric fields correctly.');return;}var weightKg=weightLbs*0.453592;var heightCm=heightIn*2.54;var bmr;if(gender==='male'){bmr=(10*weightKg)+(6.25*heightCm)-(5*age)+5;}else{bmr=(10*weightKg)+(6.25*heightCm)-(5*age)-161;}var tdee=bmr*activity;var totalCalDeficit=lossGoal*3500;var dailyDeficit=totalCalDeficit/(weeks*7);var targetCalories=tdee-dailyDeficit;var resultHtml='
';if(calcType==='tdee'){resultHtml+='Daily Maintenance: '+Math.round(tdee)+' Calories/day
';}else{resultHtml+='Daily Target: '+Math.round(targetCalories)+' Calories/day
';resultHtml+='
To lose '+lossGoal+' lbs in '+weeks+' weeks
';}if(showSteps){resultHtml+='
';resultHtml+='Step 1: BMR Calculation: '+Math.round(bmr)+' cal
';resultHtml+='Step 2: Activity Factor: x'+activity+'
';resultHtml+='Step 3: Maintenance (TDEE): '+Math.round(tdee)+' cal
';if(calcType==='target'){resultHtml+='Step 4: Required Daily Deficit: -'+Math.round(dailyDeficit)+' cal
';}resultHtml+='
';}if(targetCalories<1200&&calcType==='target'){resultHtml+='
Note: Target is below 1,200 calories. Consult a doctor before proceeding.
';}document.getElementById('answer').innerHTML=resultHtml;}

How to Use the Weight Loss Calculator

Achieving your fitness goals requires a data-driven approach. This weight loss calculator helps you bridge the gap between where you are and where you want to be by calculating your Total Daily Energy Expenditure (TDEE) and the caloric deficit required to reach your target weight. By entering your physical metrics, the tool provides a personalized daily calorie budget.

To get the most accurate results, follow these steps:

Calculation Goal
Choose whether you want to find your maintenance calories or a specific target for weight loss.
Current Weight and Height
Provide accurate measurements. Small differences in height or weight can significantly shift the Basal Metabolic Rate (BMR) calculation.
Activity Level
Be honest about your weekly movement. Most people overestimate their activity. If you work a desk job, select "Sedentary" even if you walk occasionally.
Loss Goal and Timeframe
Define how many pounds you wish to lose and the number of weeks you plan to spend achieving it. A healthy rate is generally 0.5 to 2 lbs per week.

How It Works: The Science of Weight Loss

Our weight loss calculator uses the Mifflin-St Jeor Equation, which is currently considered the most accurate standard for predicting BMR in healthy adults. The logic follows a three-step biological process:

Daily Target = TDEE – [(Weight Goal × 3500) / (Weeks × 7)]

  • BMR (Basal Metabolic Rate): The calories your body burns at rest to maintain vital functions like breathing and heart rate.
  • TDEE (Total Daily Energy Expenditure): Your BMR multiplied by an activity factor (1.2 to 1.9) representing the energy used for physical movement.
  • The 3,500 Calorie Rule: Theoretically, there are approximately 3,500 calories in one pound of body fat. To lose one pound, you must create a 3,500-calorie cumulative deficit.

Calculation Example

Example: A 35-year-old male who weighs 220 lbs, is 6 feet tall (72 inches), and has a "Moderately Active" lifestyle wants to lose 10 lbs in 10 weeks.

Step-by-step solution:

  1. Convert Weight: 220 lbs = 99.79 kg
  2. Convert Height: 72 inches = 182.88 cm
  3. Calculate BMR: (10 × 99.79) + (6.25 × 182.88) – (5 × 35) + 5 = 1,971 calories
  4. Calculate TDEE: 1,971 × 1.55 (Moderately Active) = 3,055 calories
  5. Calculate Deficit: (10 lbs × 3,500) / (10 weeks × 7 days) = 500 calories/day
  6. Result: 3,055 – 500 = 2,555 calories per day.

Common Questions

Is the 3,500 calorie rule accurate?

While the 3,500 calorie rule is a helpful guideline, modern research suggests that as you lose weight, your metabolism adapts and slows down (adaptive thermogenesis). This means you may need to recalculate your target using the weight loss calculator every 5-10 pounds lost to remain on track.

What is a safe minimum calorie intake?

Generally, it is not recommended for women to drop below 1,200 calories per day or for men to drop below 1,500 calories per day without medical supervision. Extremely low-calorie diets can lead to muscle loss, nutrient deficiencies, and gallstones.

Why is the calculator asking for my activity level?

Your BMR only accounts for survival. Your activity level determines how much extra fuel your body needs for movement. If you eat at your BMR while being active, you will lose weight faster, but you might also feel fatigued or lose muscle mass. TDEE is a better baseline for sustainable fat loss.

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